Two decades ago, Dr. Michael Reinstein was known as one of the most prolific Medicaid billers in Chicago history, once charging the taxpayer-funded program for the care of 490 patients in just five days.

In 2009, a joint Tribune-ProPublica investigation found that Reinstein had been overprescribing powerful antipsychotic drugs in Chicago nursing homes and mental health facilities, amassing a worrisome record of assembly-line care that was linked to three patients' deaths and triggered lawsuits as well as accusations of kickbacks and fraud.

Now, six months after state regulators indefinitely suspended Reinstein's medical license, federal authorities have quietly filed a criminal charge alleging Reinstein took kickbacks from a pharmaceutical company to prescribe clozapine — known as a risky drug of last resort — to patients in his care.

According to a court filing posted Thursday evening, Reinstein, 71, is scheduled to plead guilty at his arraignment Feb. 13 on one felony count.

In a telephone interview, Reinstein's attorney, Terence Campbell, said that Reinstein was "working toward resolving the issues raised by the government and hopes to put this episode behind him soon."

The criminal charge could also signal a settlement in a pending civil case brought by the U.S. attorney's office that alleged Reinstein received illegal kickbacks from pharmaceutical companies and submitted more than 140,000 false Medicare and Medicaid claims. Authorities called it the largest civil case alleging prescription medication fraud against an individual ever brought in Chicago. Reinstein potentially faces huge damages and civil penalties.

Reached by phone Thursday, Reinstein said he could not comment on the criminal charge. But he denied any payments from Teva were for prescribing clozapine, saying he earned the money from lectures he gave at medical conferences talking about the benefits of that and other anti-psychotic medications.

Reinstein also defended his history of prescribing clozapine, which is manufactured under the trade name Clozaril. He described it as a "very useful" state-of-the-art drug whose benefits can far outweigh the risks as long as patients are closely monitored.

"I think it's an under-prescribed treatment for severe mental illness," Reinstein said. "I and many other people have been involved in many research studies that show it keeps people from engaging in violent behavior … and is helpful in suicide prevention."

First licensed in Illinois in 1968, Reinstein built a lucrative practice in Chicago providing psychiatric care to mentally ill patients in nursing homes concentrated near his strip-mall office in the city's Uptown neighborhood.

Reinstein's history of improbably prolific Medicaid billing goes back to at least 1991, when he was suspended from the program for a year after officials accused him of failing to keep records to substantiate his work.

A 1993 Tribune series highlighting problems in the Medicaid system showed that in 1991 alone Reinstein had billed for 15,480 patient encounters, mostly in Chicago-area nursing homes. He claimed in bills submitted to the system that he had cared for more than 70 patients a day on 44 different days, the newspaper found. The number of patients visits topped more than 100 a day on 12 days, his bills claimed.

For years, Reinstein routinely prescribed antipsychotic and other psychiatric medications to indigent patients based on kickbacks from pharmaceutical companies, not his own independent evaluation of the patients' needs, according to the civil suit filed by prosecutors in 2012.

According to the suit, the company that originally made Clozaril paid Reinstein to promote it even as he became the largest prescriber of the drug to Medicaid recipients in the nation. In 2003, Reinstein agreed to begin prescribing a generic version made by IVAX Pharmaceuticals in exchange for a $50,000 annual "consulting agreement" that included paying his nurse to speak on behalf of the drug and funding for a Reinstein-affiliated entity known as Uptown Research Institute.

"He quickly became the largest prescriber of generic clozapine in the country," prosecutors alleged.

Between 2003 and 2006, IVAX continued to provide other perks, including flying Reinstein, his wife and seven other associates to IVAX's headquarters in Miami, where the entourage went on fishing trips, a boat cruise and golf outing.

After Israel-based Teva took over IVAX in January 2006, the company paid all expenses for Reinstein and his associates to again travel to Miami. That trip featured a $2,300 boat cruise and at least two dinners costing $1,700 each. Over the next two years, Teva paid Reinstein more than $100,000 in annual speaking fees.

Teva, also sued by federal and state officials over the alleged kickbacks to Reinstein, agreed to settle the litigation last March by paying $27.6 million. The company did not admit wrongdoing.

The Tribune-ProPublica investigation found that in 2007 Reinstein prescribed various medications to 4,141 Medicaid patients, including more prescriptions for clozapine that were written by all the doctors in Texas put together. Records from that year suggested that if each of his patient visits had lasted only 10 minutes, Reinstein would have had to work 21 hours a day, seven days a week.

Reporters also uncovered autopsy and court records showing that three patients under Reinstein's care died of clozapine intoxication between 1999 and 2007. One was Alvin Essary, who had more than five times the toxic level of clozapine in his blood when he died in 1999, medical records showed. His family sued Reinstein for negligence, claiming the doctor should not have prescribed multiple medications to a patient with one kidney. The lawsuit settled for $85,000.

Clozapine is not a commonly prescribed drug. But while Reinstein was allegedly soliciting kickbacks, he had more than half of his patients on it, according to the government. At one nursing home, he had prescribed the medication to 300 of its 400 residents, the lawsuit alleged.

Originally developed in the 1960s, clozapine has potentially severe side effects, including seizures, a decrease in white blood cells and inflammation of the heart wall. It is typically prescribed only for patients that have not responded to other treatments. Several studies, however, have lauded the drug's ability to reduce the symptoms of schizophrenia, particularly in patients who have harmed themselves in the past or attempted suicide.

In his comments Thursday to the Tribune, Reinstein said there are risks with any kind of psychiatric care — including not medicating a patient enough — and that clozapine has been unfairly portrayed as dangerous. He said he was not aware of any patient of his who had died from the drug since 2007.

"I'm not trying to be cavalier about it — anyone on Clozaril or any other psychotropic medication needs to be monitored carefully," Reinstein said. "But the drug is not by itself dangerous."